#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
#include<string>
using namespace std;
class Solution {
public:
    char dismantlingAction(string arr) {
        int ret[26] = { 0 };
        for (auto& ch : arr)
        {
            ret[ch - 'a']++;
        }
        for (auto& ch : arr)
        {
            if (ret[ch - 'a'] == 1) return ch;
        }
        return ' ';
    }
};
int main()
{
    Solution s;
    string str("leetcode");
    char ret = s.dismantlingAction(str);
    cout << ret << endl;
    return 0;
}